Free radicals in the reaction between t-butyl hydroperoxide and titanous ion: Some observations by electron spin resonance spectrometry

Mulcahy, Mfr; Steven, J. H.; Ward, Joseph P.

doi:10.1071/ch9651177

Cited by 22 publications

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“…As shown in Figure , yields of phenol and cresols, major products, are independent of equivalence ratio. Cresol is evolved via a methylcyclohexadienone intermediate formed by addition of methyl to phenoxy at the ortho or para position …”

Section: Resultsmentioning

confidence: 99%

“…These molecules possess a weak, abstractable hydrogen atom and are also polar, so abstraction could be a fast (low E a ) process. Mulcahy and Williams, in their study of methyl radical reactions with phenol, observed larger yields of CH 4 than could be accounted for by abstraction from phenol. They attributed their surplus CH 4 to an unusually rapid reaction between CH 3 and methylcyclohexadienone intermediates.…”

Section: Kinetic Modelingmentioning

confidence: 96%

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Pyrolysis and Oxidation of Anisole near 1000 K

1997

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Experiments near 1000 K have revealed the thermal decomposition of anisole to proceed exclusively via homolysis of the O-CH 3 bond. The anisole decay was observed to be first order even in the presence of oxygen. The distribution of reaction intermediates was virtually independent of equivalence ratio, φ ≡Phenol, cresols, methylcyclopentadiene, and CO were major products. Minor species included benzene, cyclopentadiene, ethane, and methane. Trace yields of ethene, toluene, and naphthalenes were observed under all conditions; trace C 2 -C 4 species including acetylene, allene, and 1,3-butadiene were observed only in the oxidation experiments. Oxidation occurs preferentially through methylcyclopentadiene. A multichannel reaction scheme is proposed involving the formation of a chemically activated adduct from phenoxy and methyl. The complex reacts to form primarily cresols and methylcyclopentadiene + CO either directly or subsequent to stabilization. A kinetic model for anisole pyrolysis has been developed to predict the disappearance of anisole and the production of reaction intermediates. Excellent agreement is obtained between experimental data and model predictions of anisole, CO, methylcyclopentadiene, and total phenolics.

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Section: Resultsmentioning

confidence: 99%

Section: Kinetic Modelingmentioning

confidence: 96%

Pyrolysis and Oxidation of Anisole near 1000 K

1997

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“…Studies of association reactions with hydrogen atoms , and methyl radicals , (yielding phenol and anisole or cresols, respectively) have been reported. Concerning the association reaction with NO, only one combined experimental and theoretical study has been performed .…”

Section: Introductionmentioning

confidence: 99%

Kinetics and Thermochemistry of the Reversible Combination Reaction of the Phenoxy Radical with NO

et al. 1998

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The kinetics of the association reaction of the phenoxy radical with NO were investigated using a flash photolysis technique coupled to UV absorption spectrometry. This yielded k(C6H5O + NO) = (1.65 ± 0.10) × 10-12 cm3 molecule-1 s-1, with no significant temperature effect over the temperature range 280−328 K. Experiments were performed at atmospheric pressure, and theoretical calculations using the RRKM method showed that the rate constant is at the high-pressure limit above ≈50 Torr for temperatures below 400 K. Upon increasing the temperature, the reaction was found to be reversible, and the equilibrium kinetics have been studied at seven temperatures between 310 and 423 K. The equilibrium constant can be expressed as ln(K c/cm3 molecule-1) = −(63.3 ± 1.0) + (10 140 ± 1000)K/T. Thermodynamic treatment of the data by the Third Law method of analysis yielded ΔH°298 = (−87.3 ± 8.0) kJ mol-1 (yielding ΔH°0 = (−83.8 ± 8.0) kJ mol-1 and ΔH°f,298(C6H5O(NO)) = (51.5 ± 8.0) kJ mol-1), corresponding to the calculated ΔS°298 = (−164.9 ± 8.0) J mol-1 K-1. All spectroscopic parameters necessary for RRKM calculations and for the entropy determination using statistical thermodynamics were calculated using both semiempirical (MNDO) and DFT methods. Influence of the resonance stabilization energy of radicals on R−NO bond dissociation energy is discussed.

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“…Both these radical-generating systems produce two radicals by way of two-step reactions (1,6,(8)(9)(10), viz., [9] and, consequently, their use is attended by an element of ambiguity in that a suitably reactive substrate may perhaps react with the unstable radical precurser of the methyl radical, (CH,),-CO(0.) or (CH,),C-0.. N o clear evidence for this sort of complication was found even in the case of the substrate acetaldoxime, for which such evidence inight be the most easily discerned on account of the likely presence of an interacting P-CH group proton in the radicals expected frdm this substrate (see above).…”

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confidence: 99%

Electron paramagnetic resonance spectroscopic study of nitroxide radicals formed from oximes

Smith¹,

Fox²

1969

Can. J. Chem.

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The addition of hydroxyl radicals to each of the oximes, acetaldoxime, acetoxime, and 2,3-butanedione monoxime, has been studied by mixing titanous chloride, hydrogen peroxide, and the oxime in a n aqueous continuous-flow system. I n each case a p-hydroxy nitroxide (functional structure )c(oH)-NH-0.) is formed. I n confirmation of these results, amino and hydroxymethyl radicals we; e added to the oximes using similar procedures to give in each case the radicals of functional structure >c(NH,)-NH-0. and )C(CH~OH)-NH-o., respectively. Attempts to add methyl radicals, prepared by the reaction betwGen titanous chloride and t-butyl hydroperoxide, to these oximes gave no observable products save the methyl radicals. However, use of titanous chloride and peracetic acid gave results consistent with the addition of hydroxyl radicals. The addition of hydroxyl radicals to the oxime-0-methyl ethers of acetaldehyde and acetone gave radicals of functional structure 'c(oH)-N-0-CH, / (JaNl, ca. 14 G ; a,,0CH3~, ca. 3 G ) which have not previously been identified unambiguously. On the assumption that JQNl = lQHNH = 23 G in all these radicals, pNn has been calculated and used to obtain a value for lQHO H~I of ca. 11 G whlch is within the range of other estimates in the literature.

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Free radicals in the reaction between t-butyl hydroperoxide and titanous ion: Some observations by electron spin resonance spectrometry

Cited by 22 publications

References 0 publications

Pyrolysis and Oxidation of Anisole near 1000 K

Pyrolysis and Oxidation of Anisole near 1000 K

Kinetics and Thermochemistry of the Reversible Combination Reaction of the Phenoxy Radical with NO

Electron paramagnetic resonance spectroscopic study of nitroxide radicals formed from oximes

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